Image forming apparatus and method with charge switching to effect power supply control

BACKGROUND OF THE INVENTION

p-00021. Field of the Invention

p-0003The present invention relates to an image forming apparatus and a method of controlling a power supply thereof. The image forming apparatus comprises a power storage unit that receives and stores electric power from an external power source such as a commercial power source, and a thermal fixing unit using electrothermally generated temperature. The image forming apparatus reduces usage of electric current from the commercial power source using electric power from both the commercial power source and the power storage unit when the thermal fixing unit is being warmed up. The image forming apparatus, in particular, has an energy saving standby mode, and the present invention relates to energy saving of power storage in the energy saving standby mode.

p-00042. Description of the Related Art

p-0005An image forming apparatus is conventionally known, that forms a toner image on a recording medium using an electrophotographic process and comprises a fixing unit which feeds the medium with the image and presses it between temperature-controlled fixing parts, thus thermally fixing the image thereupon. A method has been proposed in the image forming apparatus, in which rising time of the fixing unit, and thus time until start of printing, is shortened by supplying an increased quantity of electric power to the fixing unit. For example, a power storage unit in the image forming apparatus is installed, and electric power from both a commercial power source and the power storage unit is used when powering up the fixing unit, according to the cited reference 1 (JPA 2002-174988).

p-0006Another proposal is to use excess electric power from the commercial power source to power up the fixing unit, by using electric power charged in the power storage unit during standby mode to drive a direct current motor when the image forming apparatus is making a copy, according to the cited reference 2 (JPU H07-41023).

p-0007Another method has been proposed, in which the power storage unit is combined with an inductively heated thermal fixing unit capable of adjusting the electric power inputted into the device from the commercial power source, and then the electric power inputted into the fixing unit is increased according to the degree of excess electric power from the commercial power source.

p-0008An on demand fixing unit including a heater such as the inductive heater or the ceramic heater, may achieve a faster start up of the image forming apparatus by supplementing the electric power supply because of a rapid rise in temperature in response to the electric power inputted thereto. Such an approach allows doing away with pre-warming the fixing unit while leaving the image forming apparatus in a ready mode, i.e., a mode in which the apparatus turns ready to receive printing within a predetermined time period. It is possible, in turn, to adopt an on demand fixing control method that avoids a loss of electric power resulting from maintaining a standby temperature therewith.

p-0009Aside from the on demand fixing control method in ready mode, power saving control such as the following examples is performed in the image forming apparatus in order to reduce standby power. The apparatus informs to a host that ready status is in the negative and then turns into the standby mode, when a set amount of time required before turning into an energy saving mode has been elapsed after stopping print operation. A backlight in a display panel and a power supply for running the display are switched off. A power supply to an optional unit is switched off. A power supply for control of such aspects as lighting of a photo interrupter is switched off. An actuator power supply is turned off for such purposes as switching off an idle state current of a DC motor. A power supply to a cooling fan is turned off. An operation of a switching power supply is suspended. Clock cycles of a controller logic circuit are decreased. Thus, controls in the energy saving standby mode are performed, which achieve energy saving controls in standby mode.

p-0010It is possible for a user to change the set amount of time required before turning into an energy saving mode, aside from an initial time value that has been determined by taking energy saving standards into consideration. It would also be possible that the amount of time required before turning into an energy saving mode is zero seconds, such that the image forming apparatus would enter energy saving standby mode immediately upon completing a print job.

p-0011Following is a description, with reference to the attached drawings, of a prior art of an image forming apparatus comprising a configuration that uses electric power from both the commercial power source and the power storage unit when powering up the fixing unit, and also having a energy saving standby mode.

p-0012<figref idrefs="DRAWINGS">FIG. 12</figref> is a conceptual diagram that describes a hardware configuration of a power supply control as pertains to a conventional image forming apparatus.

p-0013Reference numeral <b>901</b> is a fixing unit, which is inductively heated when an AC power supply <b>904</b> supplies high-frequency electric power via a fixing power supply circuit <b>902</b>, and is controlled to maintain a predetermined temperature by an image process controller <b>908</b>. Reference numeral <b>903</b> is a two-converter low-voltage power supply, which receives electric power from the AC power supply <b>904</b> that is converted into primary DC voltage by a rectification circuit <b>905</b>, and outputs a 5-volt DC power supply for control and a 24-volt DC power supply for an actuator via separate insulated-type DC/DC converters <b>906</b> and <b>907</b>, respectively.

p-0014Reference numeral <b>908</b> is the image process controller, which communicates with an image forming controller <b>909</b>, which is connected to a host <b>926</b>, via a command signal <b>924</b>. The image process controller <b>908</b> synchronizes a laser driver <b>910</b>, which serves as an image forming material, a high-voltage power supply <b>914</b>, and an actuator <b>915</b>, which comprises such components as a scanner motor, a drum motor, a conveyor motor, and a solenoid fan motor, with a video signal <b>923</b>, via a well-known electrophotographic process. The synchronization draws on information of a sensor type <b>912</b>. A toner image is formed on a recording medium, and the image is pressed and fixed by the temperature controlled fixing unit <b>901</b>. Reference numeral <b>927</b> is a backlight that illuminates a display panel <b>925</b>.

p-0015Reference numeral <b>911</b> is a power saving switch, and reference numeral <b>922</b> is a signal to suspend the converter. If the image forming apparatus is not accessed via either the host <b>926</b> or the display panel <b>925</b> within a set period of time, the image forming controller <b>909</b> generates an energy saving command. Upon receipt of the energy saving command, the image process controller <b>908</b> performs power saving through interruptions and suspensions, and transitions to energy saving standby mode, with the ready signal in the negative.

p-0016Reference numeral <b>913</b> is a power storage unit, which is inserted in a supply route of the 24-volt output from the two-converter low-voltage power. In the power storage unit <b>913</b>, a charging unit <b>917</b>, for which the 24-volt power is provided, supplies a constant current to charge a capacitive unit <b>918</b>, which is constituted of an electric double layer capacitor. The capacitive unit <b>918</b> is charged until a predetermined level of charged power is reached under control of a charged power monitoring unit <b>916</b>. A power storage unit control signal <b>921</b>, issued by the image process controller <b>908</b>, stops the charging of the capacitive unit <b>918</b> and activates a DC/DC converter <b>919</b>. A discharge switch <b>920</b> switches the power supplied to various loads for image forming from the 24-volt output from the two-converter low-voltage power to a 24-volt output boosted from an output of the capacitive unit <b>918</b> by the DC/DC converter <b>919</b>. The electric power that is charged in the capacitive unit <b>918</b> is supplied as low-voltage power in place of the 24-volt output from the two-converter low-voltage power. Therefore, the AC power for the low-voltage power supply is allocated to the AC power for the power supply of the fixing unit.

p-0017The capacitive unit <b>918</b> must be charged to the necessary level of power in time for initiation of the next warm-up. Therefore, the charging rate is set to about 30 watts, which is on the order of 10% of the typical discharge rate, taking into account intermittent printing by a cold start.

p-0018<figref idrefs="DRAWINGS">FIG. 13</figref> is a conceptual diagram that describes a hardware configuration of a charging component of the power storage unit <b>913</b>.

p-0019Reference numeral <b>1001</b> is the charging component, and incorporates the charging unit <b>917</b>, the capacitive unit <b>918</b>, and the charged power monitoring unit <b>916</b>, from <figref idrefs="DRAWINGS">FIG. 12</figref>. Reference numeral <b>1002</b> corresponds to the capacitive unit, which is configured of a capacitive unit with a fully charged voltage of five volts that makes two serial connections to the electric double layer capacitor. Conventionally, the capacitive unit is known as a secondary battery that uses an electrochemical reaction, from the standpoint of electric storage capacity, and as a capacitor, from the standpoint of number of charge and discharge cycles. According to the present application, however, it is necessary to satisfy both types of performance, and thus, the electric double layer capacitor is selected, with a capacity of several dozen farads, which is tremendously larger than even an electrolytic capacitor.

p-0020Whichever method is selected, the capacitive unit achieves power storage by charging as a charging characteristic until the predetermined voltage is reached, and thus, may configure a charge circuit of a given voltage with a power supply of a predetermined voltage, per Thevenin's theorem. A power supply per Thevenin's theorem is inefficient, however, because it is slow to charge. Thus, a typical charging unit of the capacitive unit is configured of a charge circuit of a given current, employing a power supply of a higher voltage than the fully charged voltage in order to charge the capacitive unit within the time predetermined for the purpose, as well as a chopper control in order to achieve highly efficient conversion.

p-0021According to this prior art, the 24-volt power supply is routed via a switching unit <b>1004</b> and a choke coil <b>1003</b> to the capacitive unit <b>1002</b>. The voltage of the charging current is converted in a current detection resistor <b>1007</b>, compares the charging current voltage with a baseline power supply <b>1009</b> in a comparator <b>1008</b>, and pulses at a gate of a one-shot multi-vibrator <b>1006</b>. The one-shot pulse switches off the switching unit <b>1004</b>, and transmits the current, with which the choke coil <b>1003</b> is charged by a circulating diode <b>1005</b> connected to a ground, to the capacitive unit <b>1002</b>. The chopping circuit of a given current that is switched off for a given time is thus configured into the charging unit.

p-0022A hysteresis converter <b>1010</b> uses a baseline power supply <b>1011</b> to detect the voltage of the electric double layer capacitor, in order to avoid excess charging. The charged power monitoring unit is configured such that, when the detected voltage reaches five volts, a set terminal of the one-shot multi-vibrator <b>1006</b> is switched on, forcibly stopping the charge. Reference numeral <b>1012</b> is an OR gate, which inputs a forcible charge stop signal from the image process controller <b>908</b> into the set terminal of the one-shot multi-vibrator <b>1006</b>.

p-0023<figref idrefs="DRAWINGS">FIG. 14</figref> is a diagram describing power storage control at the time of printing, as pertains to the prior arts depicted in the configurations in <figref idrefs="DRAWINGS">FIGS. 12 and 13</figref>.

p-0024Reference numeral <b>1101</b> is a fixing temperature, reference numeral <b>1102</b> is the incoming AC power, reference numeral <b>1103</b> is power accumulated in the capacitor, and reference numeral <b>1104</b> is power coming into, and discharging from, the capacitor. The indicators display the charge and discharge operation of the capacitive unit for the intermittent printing that can occur during a cold start, along the same temporal axis. Reference numeral <b>1107</b> is a first discharge section and reference numeral <b>1108</b> is a second discharge section. The capacitor switches to discharge in section when activating the drum motor drives power consumption to a peak, once either of a predetermined time <b>1105</b> or <b>1106</b> has passed. Approximately 300 watts of electric power is supplied as 24-volt power to a 24-volt load. When the discharge is completed, power accumulated in the capacitor drops below a level for commencing charging <b>1112</b>, thus causing charging to take place in either a charging section <b>1109</b> or <b>1110</b> until a maximum capacitance level <b>1111</b> is reached.

p-0025The level for commencing charging <b>1112</b> is set to a first capacitance level that corresponds to a power level that is required of the capacitive unit for warm-up, and the maximum capacitance level <b>1111</b> is set to a second capacitance level that corresponds to a maximum capacitance level of the capacitive unit. A monitoring capacitance level of the charged power monitoring unit maintains the capacitance level between the first capacitance level and the second capacitance level.

p-0026The charging rate of the charging unit of the power storage unit is set to a first charging rate, which is capable of reaching the first charged power level and is determined based on time period from an end of a first warm-up, of a first intermittent print at cold start, to a start of a second warm-up, together with the amount of the discharge. The charging rate is set to about 30 watts, which is on the order of 10% of the typical discharge rate.

p-0027<figref idrefs="DRAWINGS">FIG. 15</figref> describes power storage control as pertains to energy saving standby mode in the configuration in <figref idrefs="DRAWINGS">FIGS. 12 and 13</figref>. Items in <figref idrefs="DRAWINGS">FIG. 15</figref> that describe events identical to events in <figref idrefs="DRAWINGS">FIG. 14</figref> are designated with identical reference numerals, and descriptions thereof are omitted.

p-0028Reference numeral <b>1201</b> is an expanded representation of the charging of the power coming into, and discharging from, the power storage unit. Reference numeral <b>1203</b> is section of the energy saving standby mode, in which the energy saving unit suspends power to the actuator and so on at an energy saving command generation timing <b>1202</b>. The configuration is intended to reduce power consumption only with the idle state power of the 5-volt DC power supply for control insulated-type DC/DC converter <b>906</b> of the two-converter low-voltage power supply <b>903</b>, and the sleep power and the capacitive unit's charging power of the image process controller <b>908</b> and the image forming controller <b>909</b>.

p-0029Even though power is being conserved in energy saving standby mode by powering off at predetermined loads according to the above prior arts, a charging power consumption <b>1207</b> of approximately 30 watts occurs during charging of the capacitive unit in a first charge section <b>1204</b> of the energy saving standby mode. A power consumption similar to the charging power consumption <b>1207</b> occurs even in a second charge section <b>1206</b> of the energy saving standby mode, which is a recharge operation resulting from a natural discharge of the capacitive unit. The charging power consumption in the first or second charge section is in the range of 35 watts, as compared with a normal power consumption in the range of 5 watts in a non-charge section <b>1205</b> of the energy saving standby mode, and thereby a spike arises in power consumption.

p-0030While this power consumption is small as average power consumption because of the short duration, the amount of power involved may exceed energy saving standards. It is therefore necessary as a countermeasure to stop charging during the energy saving standby mode.

p-0031Stopping recharging during the energy saving standby mode, however, causes both a natural discharge of the capacitive unit and a cool down of the fixing unit being left unattended. Consequently, either the capacitive unit is recharged or the fixing unit is warmed up without any assistance from the capacitive unit, when recovering from the energy saving standby mode to the ready mode. In either case, more time is required to recover the image forming apparatus to a print-ready mode, and thereby resulting in a loss of the on demand capability thereof.

p-0032In particular, when setting a time period short before switching to the energy saving mode, the frequency increases with which the image forming apparatus switches to the energy saving standby mode without the charged level of the capacitive unit being fully recharged. Hence, the method in which the charging of the capacitive unit is stopped in the energy saving standby mode fails to maintain the on demand capability.

SUMMARY OF THE INVENTION

p-0033An object of the present invention, to solve the above problems, is to provide an image forming apparatus and a method of controlling a power supply thereof, that are capable of charging while also avoiding to exceed energy saving power standards that may arise as a result of a projective power consumption in the energy saving standby mode.

p-0034Another object of the present invention is to provide an image forming apparatus and a method of controlling a power supply thereof that are capable of on demand fixing using power stored in the capacitive unit even when the image forming apparatus recovers from the energy saving standby mode, and avoiding a loss in charged power from a natural discharge of the capacitive unit in the energy saving standby mode.

p-0035A further object of the present invention is to provide an image forming apparatus and a method of controlling a power supply thereof that are capable of avoiding the on demand capability being lost as a consequence of recovering from the energy saving standby mode before the charger power level of the capacitive unit has been adequately restored.

p-0036To solve the problems, the image forming apparatus of the present invention is provide, which has a thermal fixing unit adapted to fix a transfer image upon a recording medium by electrothermally generated heat, and comprises; a capacitive unit adapted to accumulate electric power at a predetermined charging level; an inputted current reducing unit adapted to reduce a current inputted from an external power source using electric power charged in the capacitive unit together with electric power from the external power source, when warming up the thermal fixing unit; a first charging unit adapted to charge the capacitive unit at a first charging rate capable of recharging the capacitive unit within a warming up section; a second charging unit adapted to charge the capacitive unit at a second charging rate that is lower than the first charging rate and greater than a natural power discharge rate of the capacitive unit maintaining a charged level; and a charge switching control unit adapted to switch a power source charging the capacitive unit from the first charging unit to the second charging unit when the image forming apparatus transitions into an energy saving standby mode, and to return the power source charging the capacitive unit from the second charging unit to the first charging unit when the image forming apparatus returns from the energy saving standby mode.

p-0037The predetermined charged level includes a charging start level and a maximum charged level, and the image forming apparatus further comprises a charged level control unit adapted to maintain the charged level of the capacitive unit between the charging start level and the maximum charged level by starting charging when the charged level is below the charging start level and stopping charging when the charged level of the capacitive unit reaches the maximum charged level.

p-0038The image forming apparatus further comprises: a charged level detection unit adapted to detect the charged level of the capacitive unit in the energy saving standby mode; a discharge rate computation unit adapted to compute a discharge rate of the capacitive unit from a temporal change of the charged level detected; and an inhibit unit adapted to inhibit charging of the capacitive unit and a use of electric power discharged from the capacitive unit, when the computed discharge rate of the capacitive unit is greater than or equal to a predetermined discharge rate.

p-0039A method of controlling a power supply of an image forming apparatus having a thermal fixing unit adapted to fix a transfer image upon a recording medium by electrothermally generated heat, is also provided. The method comprises: an inputted current reducing step of reducing a current inputted from an external power source using electric power charged in a capacitive unit adapted to accumulate electric power at a predetermined charging level together with electric power from the external power source, when warming up the thermal fixing unit; a first charging step of charging the capacitive unit at a first charging rate capable of recharging the capacitive unit within a warming up section; a second charging step of charging the capacitive unit at a second charging rate that is lower than the first charging rate and greater than a natural power discharge rate of the capacitive unit maintaining the charged level; and a charge switching control step of switching a charging step of charging the capacitive unit from the first charging step to the second charging step when the image forming apparatus transitions into an energy saving standby mode, and returning the charging step of charging the capacitive unit from the second charging step to the first charging step when the image forming apparatus returns from the energy saving standby mode.

p-0040The present invention adds a second charging unit to a conventional first charging unit, and switches over to charging via the second charging unit in energy saving standby mode. As a result, the present invention charges while avoiding exceeding energy saving standards as a consequence of a projective power consumption in the energy saving standby mode. The present invention has an additional benefit of avoiding a loss in charged power from a natural discharge of the capacitive unit in the energy saving standby mode, and facilitating on demand fixing using power stored in the capacitive unit even when the image forming apparatus recovers from the energy saving standby mode.

p-0041With regard to the timing of transitioning to the energy saving standby mode, no transition is made to an energy saving state of a power consumption unit if the first charging unit is in a charge status, and the transition is made to the energy saving state and a switch is made to charging via the second charging unit, at such time as when the charged power level reaches a predetermined power level. It is thus possible to avoid a problem of losing the on demand capability as a consequence of recovering from the energy saving standby mode before the charged power level of the capacitive unit has been adequately restored.

p-0042Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

p-0043The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

p-0044<figref idrefs="DRAWINGS">FIG. 1A</figref> is a conceptual configuration diagram describing a hardware configuration of a power supply control of an image forming apparatus according to a first embodiment.

p-0045<figref idrefs="DRAWINGS">FIG. 1B</figref> is a conceptual configuration diagram describing a hardware configuration of an image processing controller according to the embodiment.

p-0046<figref idrefs="DRAWINGS">FIG. 1C</figref> is a flowchart describing an example of a conceptual process sequence of an image process controller according to the embodiment.

p-0047<figref idrefs="DRAWINGS">FIG. 2</figref> is a conceptual configuration diagram describing a hardware configuration of a charging component of a power storage unit according to the first embodiment.

p-0048<figref idrefs="DRAWINGS">FIG. 3</figref> describes a power storage control in a energy saving standby mode according to the first embodiment.

p-0049<figref idrefs="DRAWINGS">FIG. 4</figref> is a conceptual configuration diagram describing a hardware configuration of a power supply control of an image forming apparatus according to a second embodiment.

p-0050<figref idrefs="DRAWINGS">FIG. 5</figref> is a conceptual configuration diagram describing a hardware configuration of a charging component of a power storage unit according to the second embodiment.

p-0051<figref idrefs="DRAWINGS">FIG. 6</figref> is a conceptual configuration diagram describing a hardware configuration of a power supply control of an image forming apparatus according to a third embodiment.

p-0052<figref idrefs="DRAWINGS">FIG. 7</figref> is a conceptual configuration diagram describing a hardware configuration of a charging component of a power storage unit according to the third embodiment.

p-0053<figref idrefs="DRAWINGS">FIG. 8</figref> is a conceptual configuration diagram describing a hardware configuration of a charging component of a power storage unit according to a fourth embodiment.

p-0054<figref idrefs="DRAWINGS">FIG. 9</figref> describes a charging control in a energy saving standby mode according to the fourth embodiment.

p-0055<figref idrefs="DRAWINGS">FIG. 10</figref> is a circuit diagram describing an example of a configuration of a capacitive unit according to another embodiment.

p-0056<figref idrefs="DRAWINGS">FIG. 11</figref> is a circuit diagram describing an example of a configuration of a second charging unit according to another embodiment.

p-0057<figref idrefs="DRAWINGS">FIG. 12</figref> is a conceptual configuration diagram describing a conventional example of a hardware configuration of a power supply control of an image forming apparatus.

p-0058<figref idrefs="DRAWINGS">FIG. 13</figref> is a conceptual configuration diagram describing a conventional example of a hardware configuration of a charging component of a power storage unit.

p-0059<figref idrefs="DRAWINGS">FIG. 14</figref> describes a conventional example of a charging power control at printing.

p-0060<figref idrefs="DRAWINGS">FIG. 15</figref> describes a conventional example of a charging power control in the energy saving standby mode.

DESCRIPTION OF THE EMBODIMENTS

p-0061Following is a description of preferred embodiments of the present invention, with reference to the attached drawings.

First Embodiment

p-0062A first embodiment of the present invention is configured to add a second charging unit to a conventional first charging unit, and to switch over to charging via the second charging unit in energy saving standby mode, by way of providing a unit that reduces power consumption when charging a capacitive unit in energy saving standby mode. In the energy saving standby mode, a backlight in a display panel is dimmed, a power supply for running the display is switched off, a power supply to a paper feed or a paper discharge optional unit is switched off, a power supply for control of such aspects as lighting of a photo interrupter is switched off, an actuator power supply for such purposes as switching off an idle state current of an actuator, including a scanner motor, a solenoid, a stepping motor, a DC motor, and a cooling fan, is itself turned off, a converter that suspends a switching operation of a switching power supply is itself suspended, and/or a clock speed of a controller logic circuit is decreased.

Example of Configuration of Power Supply Control of Image Forming Apparatus According to First Embodiment

p-0063<figref idrefs="DRAWINGS">FIG. 1A</figref> is a conceptual configuration diagram describing a hardware configuration according to the embodiment.

p-0064Reference numeral <b>901</b> is a fixing unit which fixes a transfer image upon a recording medium with electrothermally generated temperature. The fixing unit <b>901</b> is inductively heated by supplying high-frequency electric power, which is generated from an AC power of an AC power supply <b>904</b> by a fixing power supply circuit <b>902</b>, and is controlled to remain its temperature at a predetermined temperature by an image process controller <b>908</b>.

p-0065Reference numeral <b>903</b> is a two-converter low-voltage power supply that receives electric power from the AC power supply <b>904</b> that is converted into primary DC voltage by a rectification circuit <b>905</b>, and outputs a 5-volt DC power supply for control and a 24-volt DC power supply for an actuator via separate insulated-type DC/DC converters <b>906</b> and <b>907</b>, respectively.

p-0066Reference numeral <b>908</b> is the image process controller, which communicates with an image forming controller <b>909</b>, which is connected to a host <b>926</b>, via a command signal <b>924</b>. The image process controller <b>908</b> synchronizes, as image forming parts, a laser driver <b>910</b>, a high-voltage power supply <b>914</b>, and an actuator <b>915</b> with a video signal <b>923</b> under a well-known electrophotographic process. The actuator <b>915</b> comprises such components as a scanner motor, a drum motor, a conveyor motor, and a solenoid fan motor. The synchronization control uses information of sensors <b>912</b>. A toner image is formed on a recording medium, and the image is pressed and fixed by the temperature controlled fixing unit <b>901</b>. Reference numeral <b>927</b> is a backlight that illuminates a display panel <b>925</b>.

p-0067Reference numeral <b>911</b> is a power saving switch, and reference numeral <b>922</b> is a signal to suspend the converter. If the image forming apparatus is not accessed via either the host <b>926</b> or the display panel <b>925</b> within a set period of time, the image forming controller <b>909</b> generates an energy saving command. Upon receipt of the energy saving command, the image process controller <b>908</b> performs power saving through interrupts and suspensions, and transitions to energy saving standby mode, with the ready signal in the negative.

p-0068Reference numeral <b>913</b>-<b>1</b> is a power storage unit according to the embodiment, which is inserted in a supply route of the 24-volt output of the two-converter low-voltage power supply. In the power storage unit <b>913</b>-<b>1</b>, a charging unit <b>101</b>, for which the 24-volt power is provided, supplies a constant current to charge a capacitive unit <b>918</b>, which is constituted of an electric double layer capacitor. The capacitive unit <b>918</b> is charged until a predetermined level of charged power is reached under control of a charged power monitoring unit <b>916</b>. A power storage unit control signal <b>921</b> including a stop charging signal, issued by the image process controller <b>908</b>, stops the charging of the capacitive unit <b>918</b> and activates a DC/DC converter <b>919</b>. A discharge switch <b>920</b> switches the power supplied to various loads for image forming from the 24-volt output from the two-converter low-voltage power to a 24-volt output boosted from an output of the capacitive unit <b>918</b> by the DC/DC converter <b>919</b>. The electric power that is charged in the capacitive unit <b>918</b> is supplied as low-voltage power in place of the 24-volt output from the two-converter low-voltage power. Therefore, the incoming AC power for the low-voltage power supply is reduced, and the reduced AC power for the low-voltage power supply is allocated to the AC power for the power supply of the fixing unit.

p-0069Reference numeral <b>101</b> is a first charging unit, in similar to the charging unit <b>917</b> in the conventional example, to which the 24-volt power supply is inputted and from which a constant current is used to charge the capacitive unit <b>918</b> via a charging switch relay <b>103</b>. A second charging unit <b>102</b> is provided in addition to the first charging unit <b>101</b>, according to the embodiment. The second charging unit <b>102</b> is configured to receive the output of the 5-volt DC control power supply and to charge the capacitive unit <b>918</b> with its output via the charging switch relay <b>103</b> as a switching unit.

Example of Configuration of Image Process Controller

908

p-0070<figref idrefs="DRAWINGS">FIG. 1B</figref> is a block diagram depicting an example of a configuration of the image processing controller <b>908</b> depicted in <figref idrefs="DRAWINGS">FIG. 1A</figref>. While <figref idrefs="DRAWINGS">FIG. 1B</figref> depicts an example that implements control in software, it would also be possible to implement control via a hardware configuration. It would also be permissible for control to be shared with the image forming controller <b>909</b> in <figref idrefs="DRAWINGS">FIG. 1A</figref>. <figref idrefs="DRAWINGS">FIG. 1B</figref> depicts a configuration that is closely related to the embodiment, with other elements being omitted.

p-0071The image process controller <b>908</b> comprises a CPU <b>9081</b> for computational control, which controls the image forming process, and a communications controller <b>9082</b>, which controls communication with the image forming controller <b>909</b>. The CPU <b>9081</b> comprises a timer <b>9081</b><i>a</i>, which keeps track of time.

p-0072The image process controller <b>908</b> also comprises a ROM <b>9083</b>, which stores programs that the CPU <b>9081</b> executes and data, and a RAM <b>9084</b>, which serves as a temporary storage area while the CPU <b>9081</b> is in operation.

p-0073The ROM <b>9083</b> stores an image process control program <b>9083</b><i>a</i>, which is related to the embodiment, as well as an energy saving control module <b>9083</b><i>b </i>and a charge and discharge control module <b>9083</b><i>c</i>, which are embedded within the image process control program <b>9083</b><i>a</i>. Also stored in the ROM <b>9083</b> are such elements as a fixing start-up time (t<b>1</b>) <b>9083</b><i>e </i>and a drum motor drive time (t<b>2</b>) <b>9083</b><i>f</i>, as various timing parameters <b>9083</b><i>d</i>. The ROM <b>9083</b> additionally stores a setting temperature (Th) <b>9083</b><i>g </i>of the fixing unit, as well as a first and second charging levels <b>9083</b><i>h</i>, which are used in <figref idrefs="DRAWINGS">FIG. 8</figref>, according to a fourth embodiment.

p-0074The RAM <b>9084</b> maintains a plurality of flags <b>9084</b><i>a </i>through <b>9084</b><i>d</i>, which signify forking during the execution of image process control program <b>9083</b><i>a</i>. The RAN <b>9084</b> also maintains a space for a current process sequence <b>9084</b><i>e</i>, a current fixing unit temperature (T(t)) <b>9084</b><i>f</i>, and a current charge voltage <b>9084</b><i>g</i>, which is used according to the fourth embodiment. The above flags <b>9084</b><i>a </i>through <b>9084</b><i>d </i>are a flag <b>9084</b><i>a </i>that indicates whether or not the energy saving standby mode is set, a flag <b>9084</b><i>b </i>that indicates to force to stop charging, a discharge flag <b>9084</b><i>c</i>, and a flag <b>9084</b><i>d </i>that indicates whether the first charging unit or the second charging unit is used. The flags <b>9084</b><i>a </i>through <b>9084</b><i>d </i>correspond to signals that control such elements as the power storage unit <b>913</b>-<b>1</b>, the insulated-type DC/DC converter <b>907</b>, and the power saving switch <b>911</b>.

p-0075The RAM <b>9084</b> also comprises an I/O interface <b>9085</b> that interfaces with output of signals that control respective elements, as well as input of information that denotes statuses of an apparatus.

p-0076The energy saving mode signal <b>922</b> is outputted via the I/O interface <b>9085</b> to the insulated-type DC/DC converter <b>907</b>, and a charge control signal <b>921</b><i>a </i>is outputted via the I/O interface <b>9085</b> to the charging switch relay <b>103</b>. A discharge control signal <b>921</b><i>b </i>is outputted via the I/O interface <b>9085</b> to the discharge switch <b>920</b>, a forcible charge stop signal <b>921</b><i>c </i>is outputted via the I/O interface <b>9085</b> and a power saving control signal is outputted via the I/O interface <b>9085</b> to the power saving switch <b>911</b>. A temperature from the fixing unit <b>901</b> is inputted via the I/O interface <b>9085</b>, and a charging potential level <b>1301</b>, which is used according to the fourth embodiment, is inputted via the I/O interface <b>9085</b> from the capacitive unit <b>918</b>.

Example of Operation of Image Process Controller

908

p-0077<figref idrefs="DRAWINGS">FIG. 1C</figref> is a flowchart describing an example of a control sequence of the image process controller <b>908</b> depicted in <figref idrefs="DRAWINGS">FIG. 1A</figref>. The flowchart depicts only an operation that is related to the embodiment, but other elements are omitted. It would be permissible for the flowchart to be contained within a control of another image process, or to be executed in parallel thereto.

p-0078The CPU <b>9081</b> repeatedly loops through the flowchart in <figref idrefs="DRAWINGS">FIG. 1C</figref> in response to an interrupt at a start of printing. The flowchart begins with the execution of a predetermined process in accordance with the image process control. Initially, the charging switch relay <b>103</b> is connected to the first charging unit <b>101</b>, and the discharge switch <b>920</b> is connected to the insulated-type DC/DC converter <b>907</b>.

p-0079A judgment is made in step S<b>11</b> as to whether or not the image process control has reached the fixing start-up timing (t<b>1</b>). If having reached the fixing start-up timing (t<b>1</b>), the process proceeds to step S<b>12</b>, in which the fixing power supply is switched on and the fixing unit is heated up.

p-0080A judgment is made in step S<b>13</b> as to whether or not the image process control has reached the drum motor driving start time (t<b>2</b>). If having reached the drum motor driving start time (t<b>2</b>), the process proceeds to step S<b>14</b>, in which the forcible charge stop signal is set to on. In step S<b>15</b>, the discharge switch <b>920</b> is connected to the DC/DC converter <b>919</b>, and the output of the capacitive unit <b>918</b> is supplied versus the load after being boosted from 5 to 24 volts. The drum motor is driven in step S<b>16</b>.

p-0081A judgment is made in step S<b>17</b> as to whether or not the fixing temperature has reached the target temperature Th. If having reached the target temperature Th, the process proceeds to step S<b>18</b>, in which the discharge switch <b>920</b> is disconnected from the DC/DC converter <b>919</b> and then reconnected to the insulated-type DC/DC converter <b>907</b>. The forcible charge stop signal is switched off in step S<b>19</b>, to automatically start charging in accordance with the charged power monitoring unit <b>916</b>.

p-0082A judgment is made in step S<b>20</b>, in the charging process, as to whether or not the current mode of the image forming apparatus is the energy saving standby mode. If in the energy saving standby mode, the charging switch relay <b>103</b> is connected to the second charging unit <b>102</b>, and charging starts using the 5-volt DC control power supply from the insulated-type DC/DC converter <b>906</b>. If not in the energy saving standby mode, the charging switch relay <b>103</b> is connected to the first charging unit <b>101</b>, and charging starts using the 24-volt power supply from the insulated-type DC/DC converter <b>907</b>.

Example of Hardware Configuration of Charging Component of Power Storage Unit

913

-

1

According to First Embodiment

p-0083<figref idrefs="DRAWINGS">FIG. 2</figref> is a conceptual configuration diagram describing a hardware configuration of a charging component of the power storage unit <b>913</b>-<b>1</b> depicted in <figref idrefs="DRAWINGS">FIG. 1A</figref>.

p-0084Reference numeral <b>101</b> is a first charging unit. In order to simplify the description, the first charging unit <b>101</b> also includes the capacitive unit <b>918</b> and the charged power monitoring unit <b>916</b>, in addition to the charging unit <b>101</b> in <figref idrefs="DRAWINGS">FIG. 1A</figref>. The first charging unit <b>101</b> is identical to the charging component <b>1001</b> in the conventional example depicted in <figref idrefs="DRAWINGS">FIG. 13</figref>, and thus, a description thereof will be avoided herein.

p-0085The first charging unit <b>101</b> is configured of a chopper constant current circuit that has the same 24-volt power supply as the charging unit <b>917</b> in the conventional example, such that it is possible to charge the power storage unit in highly efficient conversion rate within a predetermined time. The second charging unit <b>102</b> comprises a backflow blocking diode <b>201</b> and a maximum current setting resistor <b>202</b>, and configures a constant voltage charging circuit with a charge voltage of 5 volts. Although the constant voltage charging circuit may incur such disadvantages as loss of charge due to resistance or speed of charging, it is applied as a charging unit to compensate a natural discharge from the capacitive unit <b>1002</b>. The charging voltage is made the same 5 volts as the fully charged voltage of the capacitive unit <b>1002</b>, and then a charging characteristic is set so that the smaller the charge current is the nearer the charging voltage approaches the fully charged voltage. Therefore, it is possible to provide a charging unit that has highly reliable protecting against excess charge and thus incurs no current loss due to switching.

Example of Operation of Power Supply Control of Image Forming Apparatus According to the First Embodiment

p-0086<figref idrefs="DRAWINGS">FIG. 3</figref> describes a power storage control in a energy saving standby mode in the above mentioned hardware configuration according to the first embodiment.

p-0087Reference numeral <b>1101</b> is a fixing temperature, reference numeral <b>1102</b> is the incoming AC power, reference numeral <b>1103</b> is power charged in the capacitive unit, and reference numeral <b>1201</b> is power charged into and discharged from the capacitive unit. The charging and discharging power <b>1201</b> indicates the charge and discharge operation of the capacitive unit for the intermittent printing occurring in a cold start, along the same time axis. Reference numeral <b>1107</b> is a discharge section. The power storage unit switches to discharge during the discharge section <b>1107</b>, in which power consumption goes to a peak by activating the drum motor after a predetermined time <b>110</b> has been elapsed from starting up of the mixing unit. Approximately 300 watts of electric power is supplied as 24-volt power to 24-volt loads. When the discharge is finished, power charged in the capacitive unit drops below a start charging level <b>1112</b>, and thus charging is performed until a maximum charged level <b>1111</b> is reached. The start charging level <b>1112</b> is set to a first charged level that corresponds to a power level required for warm-up of the capacitive unit, and the maximum charged level <b>1111</b> is set to a second charged level that corresponds to a maximum charged level of the capacitive unit. A monitoring charge level of the charged power monitoring unit maintains the charged level between the first charged level and the second charged level.

p-0088The charging power of the charging unit in the power storage unit is set to a first charging rate, which is determined to enable to reach the first charged level based on a time from an end of a first warm-up in a first intermittent print at cold start to a start of a second warm-up and the amount of the discharged power. The charging rate is set to about 30 watts, which is on the order of 10% of the typical discharge rate.

p-0089Reference numeral <b>301</b> is a timing at which the energy saving command is generated. When the energy saving command is issued by the image forming controller <b>909</b> and received by the image process controller <b>908</b>, the power saving unit is activated, such as the shutting off of power to the actuator, and the status flag <b>9084</b><i>a </i>of the image process controller <b>908</b> is set to the energy saving standby mode. The status is maintained during a section <b>302</b> of a energy saving standby mode. When the status flag <b>9084</b><i>a </i>is set to the energy saving standby mode, the image process controller <b>908</b> switches to the charging switch relay <b>103</b>. As a result, charging power <b>306</b> and <b>307</b> to the power storage unit are reduced from a constant current charging rate of the first charging unit <b>101</b> to a constant voltage charging rate of the second charging unit <b>102</b>, for a first charging section <b>303</b> and a second charging section <b>305</b>. Therefore, in the energy saving standby mode, recovery to the maximum charged level <b>1111</b> and recovery after the charged level has been below the charging start level through natural power discharge from the capacitive unit <b>1002</b> maintaining the charged level.

Benefits of the First Embodiment

p-0090The controls allow reducing power consumption in the first charging section <b>303</b> and the second charging section <b>305</b> to a level near a power consumption level that applies during a non-charging section <b>304</b>, while maintaining a charged level required in the energy saving standby mode.

p-0091It is thus possible to maintain the on demand capability within the energy saving standby mode. It is also possible thereby to reduce the power consumption in the standby mode to a sum of the idle power of the insulated-type DC/DC converter <b>906</b>, the sleep power of the image process controller <b>908</b> and the image forming controller <b>909</b>, and the charging power in the constant voltage charging power rate for the capacitive unit.

Second Embodiment

p-0092With regard to a second embodiment, the second charging unit, which reduces power consumption for charging during the energy saving standby mode, is configured by a constant voltage charging circuit to which an AC impedance unit is applied under a chopper control. The second embodiment is characterized by removing a fall in efficiency caused by a current limit resistance, which is a weakness of the constant voltage charge, by switching the charging voltage to change the charging rate of the first charging unit, and thus providing the charging characteristic that is an advantage of the constant voltage charge in a simple configuration.

Example of Configuration of Power Supply Control of Image Forming Apparatus According to Second Embodiment

p-0093<figref idrefs="DRAWINGS">FIG. 4</figref> is a conceptual configuration diagram describing a hardware configuration according to the second embodiment. Configurations according to the second embodiment comprising functions identical to configurations according to the first embodiment are designated with identical reference numerals, and descriptions thereof are omitted. Whereas an example of the present invention using a two-converter low-voltage power supply is described according to the first embodiment, an example using a single converter low-voltage power supply according to the second embodiment will be described.

p-0094Reference numeral <b>405</b> is a single converter low-voltage power supply, which outputs a 24-volt DC via an insulated-type DC/DC converter <b>403</b>. Reference numeral <b>404</b> is a non-insulated-type DC/DC converter, which converts the 24-volt DC into a 5-volt control DC. It is possible to configure the single converter low-voltage power supply less expensively than the two-converter low-voltage power supply because the non-insulated-type DC/DC converter is configured less expensively and more efficiently than the insulated-type DC/DC converter.

p-0095Reference numeral <b>406</b> is a field effect transistor (FET) energy saving switch. It is not possible in the single converter low-voltage power supply to stop an operation of the insulated-type DC/DC converter <b>403</b> and cut off the 24-volt output, as would be possible with the two-converter low-voltage power supply. Because the single converter low-voltage power supply makes the 5-volt control DC from the 24-volt DC. Consequently, in the energy saving standby mode, the FET energy saving switch is cut off and thereby the 24-volt DC output for the actuator load is switched off.

p-0096Reference numeral <b>913</b>-<b>2</b> is a power storage unit according to the embodiment, which is inserted into a route of supplying the 24-volt DC output and the 5-volt DC output from the single converter low-voltage power supply. The charging unit <b>401</b> performs constant current charging to the capacitive unit <b>918</b>, which is formed from the electric double layer capacitor, using the 24-volt DC and the 5-volt DC as the power source. Electric power is thus charged under control of a charged power monitoring unit <b>916</b> until a predetermined charged level is reached. The power storage unit control signal <b>921</b>, issued by the image process controller <b>908</b>, activates the DC/DC converter <b>919</b>. A discharge switch <b>920</b> switches the output power of the power storage unit from the low-voltage 24-volt output to a 24-volt output boosted from the voltage of the capacitive unit <b>918</b>, and the electric power charged in the capacitive unit <b>918</b> is supplied as low-voltage power to the loads in place of the power of the low-voltage power supply. Thus, the incoming AC power to the low-voltage power supply is reduced, and thereby a larger amount of power in the AC power supply <b>904</b> can be allocated to the fixing power supply.

p-0097Reference numeral <b>401</b> is the charging unit, which receives power from the 24-volt power supply and the 5-volt power supply and uses the constant voltage output thereof to charge the capacitive unit <b>918</b> at a constant voltage.

Example of Hardware Configuration of Charging Component of Power storage unit

913

-

2

According to Second Embodiment

p-0098<figref idrefs="DRAWINGS">FIG. 5</figref> is a conceptual configuration diagram describing a hardware configuration of a charging component of the power storage unit <b>913</b>-<b>2</b> depicted in <figref idrefs="DRAWINGS">FIG. 4</figref>. Configurations depicted in <figref idrefs="DRAWINGS">FIG. 5</figref> comprising functions identical to configurations depicted in <figref idrefs="DRAWINGS">FIG. 4</figref> are designated with identical reference numerals, and descriptions thereof are omitted.

p-0099Reference numeral <b>401</b> is the charging unit, in which the charging voltage is switched in line with the on/off state of the 24-volt output for the actuator load by way of a charging rate switch diode <b>402</b>. In the charging unit <b>401</b>, the charging rate is switched by switching the charging voltage in the constant voltage charging. Thus, the switching of the charging voltage implements a function of switching between the first charging unit and the second charging unit.

p-0100The charging unit <b>401</b> according to the second embodiment, which includes the first charging unit and the second charging unit, is not the same as the chopper constant current circuit according to the conventional example or the first embodiment. That is, a clock signal <b>407</b> is issued from the image process controller <b>908</b> and received by a gate circuit <b>501</b> comprising a NAND gate, and the switching unit <b>1004</b> is switched by a fixed duty ratio, rather than controlling the duty ratio by which the switching unit <b>1004</b> is switched on. The gate circuit <b>501</b> gates the clock signal <b>407</b> by an electric power stop signal <b>502</b> when the hysteresis converter <b>1010</b> detects a predetermined charged voltage, and thereby the switching unit <b>1004</b> is turned off.

Benefits of the Second Embodiment

p-0101Given the present configuration, a voltage differential between the charging voltage and the charged voltage of the capacitive unit <b>1002</b> is applied to the both ends of the choke coil <b>1003</b> by the fixed duty ratio. The AC impedance unit is configured such that the charging current is changed since the choke coil <b>1003</b> is charged currently in accordance with the voltage differential. The combination of the AC impedance unit by way of the switching operation and the power supply is the constant voltage charge circuit. Thus, the second embodiment removes a fall in efficiency caused by a current limit resistance, which is a weakness of the constant voltage charge, by switching the charging voltage to change the charging rate of the first charging unit, and thus provides the charging characteristic that is an advantage of the constant voltage charge in a simple configuration. Accordingly, a constant voltage charge operation, which could not be applied for efficiency reasons because of a conventional large charging current, can be applied to the first charging unit. The second charging unit is configured by a parameter switching unit that decreases the charging rate by switching the charging voltage to 5 volts in the energy saving standby mode, and thereby the power consumption in the standby mode can be reduced.

p-0102A unique benefit according to the second embodiment is to avoid a problem arises when charging the capacitive unit comprising the capacitors in the constant current charging method, due to applying the constant current charging method to the first charging unit that is the charging unit not in the energy saving standby mode. The problem that the charging speed in the initial charging falls because the charging power changes proportionally to the charged voltage can be avoided, therefore, the second embodiment has the effect of allowing widespread use of the charged range of the electric double layer capacitor.

Third Embodiment

p-0103According to a third embodiment, the second charging unit as the charge power consumption reduction unit in the energy saving standby mode is configured as the constant voltage charge circuit using an external power source such as the commercial power source as the power supply. Thus, the third embodiment allows charging when the switching power supply is off as well as in the energy saving standby mode.

Example of Hardware Configuration of Power Supply Control of Image Forming Apparatus According to the Third Embodiment

p-0104<figref idrefs="DRAWINGS">FIG. 6</figref> is a conceptual configuration diagram describing a hardware configuration according to the third embodiment. Configurations depicted in <figref idrefs="DRAWINGS">FIG. 6</figref> comprising functions identical to configurations depicted in <figref idrefs="DRAWINGS">FIG. 1</figref>, according to the first embodiment, and <figref idrefs="DRAWINGS">FIG. 4</figref>, according to the second embodiment, are designated with identical reference numerals, and descriptions thereof are omitted.

p-0105A power source switch <b>928</b> as an on/off unit of the low-voltage power source directly opens and closes a primary current route from the commercial power source according to the first and second embodiment. According to the third embodiment, an example of applying a power supply remote switch <b>603</b> to the low-voltage power source will be described.

p-0106Reference numeral <b>603</b> is a power supply remote switch. Rather than directly cutting off the primary current route of the commercial power source, power control is instead assigned to the image process controller by a detection signal of the power supply remote switch <b>603</b>. A separating operation of the fixing unit and a power down sequence such as the cooling sequence by the fan are then carried out. By stopping a switching operation of an inverter in an insulated-type DC/DC converter <b>602</b> and preventing transmission of electric power to a secondary side of an insulated transformer, thereafter the power supply is stopped.

p-0107With such a printer, the primary current route of the commercial power source is not cut off even if the power supply remote switch <b>603</b> is off.

p-0108Reference numeral <b>601</b> is the second charging unit, which takes the commercial power source as the power supply thereof and is connected to the capacitive unit <b>918</b> of a power storage unit <b>913</b>-<b>3</b>. It is therefore possible to charge the capacitive unit <b>918</b> by the second charging unit <b>601</b> when the switching power supply is off as well as in the energy saving standby mode.

Example of Hardware Configuration of Charging Component of Power storage unit

913

-

3

According to the Third Embodiment

p-0109<figref idrefs="DRAWINGS">FIG. 7</figref> is a conceptual configuration diagram describing a hardware configuration of a charging component of the power storage unit <b>913</b>-<b>3</b> depicted in <figref idrefs="DRAWINGS">FIG. 6</figref>.

p-0110Reference numeral <b>101</b> is the first charging unit, and incorporates not only the charging unit <b>917</b> in <figref idrefs="DRAWINGS">FIG. 1</figref>, but also the capacitive unit <b>918</b> and the charged power monitoring unit <b>916</b>, for purposes of simplicity in description. The first charging unit <b>101</b> is identical to the charging component <b>1001</b> depicted in <figref idrefs="DRAWINGS">FIG. 12</figref> of the conventional example, and therefore, a description will be omitted herein.

p-0111Reference numeral <b>601</b> is the second charging unit, which takes a commercial power source <b>702</b> as the power supply thereof and reduces the commercial power voltage 1/33 by way of an insulated transformer <b>701</b> serving as an insulated transformer unit. Reference numeral <b>703</b> is a bridge diode, which forms an insulated constant voltage charge circuit together with a current limiting resistor <b>704</b> and a Zener diode <b>705</b> protecting against excessive voltage.

Benefits of the Third Embodiment

p-0112Given the third embodiment, in the energy saving standby mode, when stopping the switching of the first charging unit <b>101</b> charging by the second charging unit <b>601</b> is switched to. It is therefore possible to charge the capacitive unit <b>918</b> by the second charging unit when the switching power supply is off as well as in the energy saving standby mode.

p-0113A unique benefit according to the third embodiment is that on demand control using the capacitive unit immediately upon switching on the power supply will be allowed by performing an extremely small charging even when the power supply is off.

Fourth Embodiment

p-0114According to the first through the third embodiments, the charging start level <b>1112</b> and the maximum charged level <b>1111</b> are set in a form of hardware in the hysteresis converter <b>1010</b>. A configuration was described, in which the first and the second charging unit perform charging and discharging control asynchronously to the timing <b>301</b> at which the energy saving command is generated. In contrast, a control unit controls switching from the first charging unit to the second charging unit according to the fourth embodiment.

Example of Hardware Configuration of Charging Component of Capacitor According to the Fourth Embodiment

p-0115As depicted in <figref idrefs="DRAWINGS">FIG. 8</figref>, the hardware configuration according to the fourth embodiment extracts the charged voltage of the capacitive unit as depicted in <figref idrefs="DRAWINGS">FIG. 5</figref> according to the second embodiment, as the charged potential level <b>1301</b>, which is in turn inputted into an A/D port of the image process controller <b>908</b> and targeted for control by the CPU <b>9081</b>. The circuit according to the forth embodiment is not limited thereto, however, provided that the configuration is present.

Example of Operation of Power Supply Control of Image Forming Apparatus According to the Fourth Embodiment

p-0116Characteristics according to the fourth embodiment are detecting the charged level and controlling the switching of the charging in accordance with the result of the detection. Accordingly, following is a description of the operation of changing the charged level and the control thereof, which are described in a control description diagram in <figref idrefs="DRAWINGS">FIG. 9</figref>.

p-0117The image process controller <b>908</b> suspends transitioning to an energy saving state of a power consumption unit if the charged level by the first charging unit is less than or equal to the charging start level <b>1112</b> on the timing <b>301</b> at which the energy saving command is inputted by the image forming controller <b>909</b>. During a section <b>801</b> while the transition to the energy saving standby mode is suspended, charging by the first charging unit continues until the charged level has reached the charging start level <b>1112</b>. When the charged level has reached the charging start level <b>1112</b>, the transition to the power saving status is performed, a energy saving standby mode flag is stored in a storage unit, and a charging is performed by the second charging unit during a section <b>802</b>.

p-0118The suspension of transitioning to an energy saving state of the power consumption unit is performed by a timing control of cut-off of the FET energy saving switch <b>406</b> in <figref idrefs="DRAWINGS">FIG. 4</figref> at the power storage unit <b>401</b> as shown in <figref idrefs="DRAWINGS">FIG. 8</figref>. For example, it may be performed by judging an output from the capacitive unit <b>1002</b> of the power storage unit <b>913</b>-<b>1</b> in <figref idrefs="DRAWINGS">FIG. 1</figref> by the image process control unit <b>908</b> and then controlling a switching timing of the charging switch relay <b>103</b>.

p-0119The charging start level <b>1112</b> is set to the first charging level, which is the quantity of electric power required for the warm-up. The unit that controls the transition to the energy saving standby mode is thus installed in order to ensure that the charge level on the transition to the energy saving standby mode has been greater than or equal to the quantity of electric power required for the warm-up.

p-0120Such action by way of the unit controlling the transition to the energy saving standby mode ensures on demand mixing control on waking up from the energy saving standby mode, regardless of whenever the energy saving command is inputted.

Other Embodiments

p-0121The preceding embodiments are some of possible examples. It would also be permissible to have a configuration that adds the second charging unit having the different charging rate to the first charging unit capable of recharging within the warm-up section, and that switches to the second charging unit in response to the status flag of the energy saving standby mode.

p-0122For example, in place of the electric double layer capacitor, as depicted in <figref idrefs="DRAWINGS">FIG. 10</figref>, it would be permissible to combine a capacitor <b>1401</b> such as an electrolytic capacitor with a secondary battery <b>1402</b> such as a proton polymer battery or a nickel hydride battery. It would also be permissible for the first charging unit to be a constant power charging unit comprising a current limiter function though admittedly expensive.

p-0123While the insulated transformer unit of the second charging unit using the commercial power source as the power supply thereof is used according to the third embodiment, it would be permissible to serially connect three or more ceramic capacitors in safety-standard <b>1501</b>, and thereby rectify a partial voltage output.

p-0124According to the embodiment, it was possible to charge in the energy saving standby mode by way of the second charging unit. Accordingly, a problem with the capacitive unit owing to increase of a current leak can be detected promptly by comparing a charge clock cycle, reference numeral <b>304</b> in <figref idrefs="DRAWINGS">FIG. 9</figref>, in which the discharge rate of the capacitive unit is minimum state with a standard clock cycle, according to the fourth embodiment. Thus, it would be permissible to configure a fault detection and control unit of the capacitive unit that performs a stop of the charging and discharging of the capacitive unit and restriction of the fixing unit warm-up power. That is, the charged level of the capacitive unit in the energy saving standby mode is detected. Next, a discharge rate of the capacitive unit from a temporal change of the charged level detected is computed. The charging of the capacitive unit as well as a use of electric power discharged from the capacitive unit are inhibited, when the discharge rate of the capacitive unit computed is greater than or equal to a predetermined discharge rate.

p-0125The present invention thus reduces the charging power consumption of the capacitive unit in the energy saving standby mode, by adding the second charging unit to the first charging unit capable of recharging within the warm-up section and switching from the first charging unit to the second charging unit in response to the status flag of the energy saving standby mode.

p-0126The present invention may be applied to a system configured of a plurality of devices, such as a computer, an interface device, a reader, and a printer, for example, as well as an apparatus configured of a single device, such as a multi-function peripheral, a printer, or a fax machine.

p-0127It is to be understood that the objectives of the present invention are achieved by using a recording medium or a storage medium that records a software program code that implements the functions of the embodiments. It is to be understood that, in such a circumstance, the objectives of the present invention are achieved by supplying the recording medium to the system or the apparatus, and the computer, or the CPU or the MPU, of the system or the apparatus loads and executes the program code that is stored on the recording medium. In such a circumstance, the program code itself that is thus loaded from the recording medium implements the functions of the embodiments, and the recording medium that records the program configures the present invention.

p-0128The functions of the embodiments are implemented by the execution by the computer of the program code thus loaded. An operating system (OS) or other software that runs on the computer performs actual processing, in whole or in part, in accordance with the instructions of the program code. It is to be understood that a circumstance wherein the functions of the embodiments are implemented by the processing thereof is also included.

p-0129The program code that is loaded from the recording medium is written to a memory that is a part of an expansion card that is inserted into a computer, or an expansion unit that is connected to a computer. It is to be understood that a circumstance wherein the CPU or other hardware that is a part of the expansion card or the expansion unit performs actual processing, in whole or in part, in accordance with the instructions of the program code, and that the functions of the embodiments are implemented by the processing thereof, is also included.

p-0130Also included within the present invention is a form wherein the functions of the embodiments are implemented by having the program data that implements the functions of the embodiments be downloaded onto the apparatus from either a CD-ROM that is placed into the apparatus, or from an external source of supply such as the Internet/World Wide Web.

p-0131When applying the present invention to the recording medium, it is desirable that the program code that is stored on the recording medium support the flowcharts described herein.

p-0132While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

p-0133This application claims the benefit of Japanese Patent Application No. 2006-261413, filed on Sep. 26, 2006, which is hereby incorporated by reference herein in its entirety.